Mask and method of forming the same

ABSTRACT

A mask includes a reflective layer, an absorption layer and an absorption part. The absorption layer is disposed over the reflective multilayer. The absorption part is disposed in the reflective layer and the absorption layer, wherein an entire top surface of the absorption part is substantially flush with a top surface of the absorption layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of and claims thepriority benefit of U.S. application Ser. No. 17/100,970, filed on Nov.23, 2020, now allowed, which is a continuation application of and claimsthe priority benefit of U.S. application Ser. No. 15/992,203, filed onMay 30, 2018, now issued as U.S. Pat. No. 10,845,698. The entirety ofeach of the above-mentioned patent applications is hereby incorporatedby reference herein and made a part of this specification.

BACKGROUND

Photolithography is utilized in the fabrication of semiconductor devicesto transfer a pattern onto a wafer. Based on various integrated circuit(IC) layouts, patterns are transferred from a photomask (or a reticles)to a surface of the wafer. As dimensions decrease and density in ICchips increases, resolution enhancement techniques, such as opticalproximity correction (OPC), off-axis illumination (OAI), double dipolelithography (DDL) and phase-shift mask (PSM), are developed to improvedepth of focus (DOF) and therefore to achieve a better pattern transferonto the wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the criticaldimensions of the various features may be arbitrarily increased orreduced for clarity of discussion.

FIG. 1A is a top schematic view of a mask in accordance with someembodiments of the disclosure.

FIG. 1B is a schematic cross-sectional view of a mask in accordance withsome embodiments of the disclosure.

FIG. 2 is a flow chart of a method of fabricating a mask in accordancewith some embodiments of the disclosure.

FIGS. 3A-3E are schematic cross-sectional views illustrating a method offabricating a mask in accordance with some embodiments of thedisclosure.

FIG. 4 is a flow chart of a method of fabricating a mask in accordancewith some embodiments of the disclosure.

FIG. 5 is a top schematic view of a wafer that is exposed using the maskof FIGS. 1A and 1B in accordance with some embodiments of thedisclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the disclosure. These are, of course, merely examplesand are not intended to be limiting. For example, the formation of asecond feature over or over a first feature in the description thatfollows may include embodiments in which the second and first featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the second and first features,such that the second and first features may not be in direct contact. Inaddition, the disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath”, “below”, “lower”,“on”, “over”, “overlying”, “above”, “upper” and the like, may be usedherein for ease of description to describe one element or feature'srelationship to another element(s) or feature(s) as illustrated in thefigures. The spatially relative terms are intended to encompassdifferent orientations of the device in use or operation in addition tothe orientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

The advanced lithography process, method, and materials described in thecurrent disclosure can be used in many applications, including fin-typefield effect transistors (FinFETs). For example, the fins may bepatterned to produce a relatively close spacing between features, forwhich the above disclosure is well suited. In addition, spacers used informing fins of FinFETs can be processed according to the abovedisclosure.

FIG. 1A is a top schematic view of a mask in accordance with someembodiments of the disclosure, and FIG. 1B is a schematiccross-sectional view of a mask of FIG. 1A along the A-A′ line inaccordance with some embodiments of the disclosure. FIG. 1B has beensimplified for the sake of clarity to better understand the inventiveconcepts of the present disclosure. Additional features can be added inthe mask, and some of the features described below can be replaced oreliminated for additional embodiments of the mask.

Referring to FIGS. 1A and 1B, in some embodiments, a mask 10 is areflective mask. In some embodiments, the mask 10 is configured tominimize reflectivity of light, particularly extreme ultraviolet (EUV)radiation (for example, EUV radiation having a wavelength of about 1 nmto about 10 nm, although other wavelengths of light (radiation) arecontemplated by the present disclosure). In some embodiments, the mask10 is a phase shift mask, such as an attenuated phase shift mask(AttPSM). Alternatively, the phase shift mask is an alternating phaseshift mask (AltPSM). The mask 10 includes a mask image region 20 and amask frame region 30. The mask image region 20 is an area of the mask 10that includes a pattern (or design) of a layer of an integrated circuitdevice (or chip). For example, the mask 10 includes a pattern (ordesign) of a layer of a resistor, a capacitor, an inductor, a diode, ametal-oxide-semiconductor field effect transistor (MOSFET), acomplementary MOS (CMOS) transistor, a bipolar junction transistor(BJT), a laterally diffused MOS (LDMOS) transistor, a high power MOStransistor, a fin-like field effect transistor (FinFET), otherintegrated circuit component, or combination thereof. The mask frameregion 30 is an area of the mask 10 that does not include the pattern(or design) of the layer of the integrated circuit device (or chip). Themask frame region 30 may include patterns (or designs) that definealignment marks (also referred to as fiducial marks). The mask frameregion 30 borders the mask image region 20, and in some embodiments, themask frame region 30 surrounds the mask image region 20, defining themask image region 20 of the mask 100. The mask 10 further includes amask black border region 32, which is an area of the mask 10 outside themask image region 20 that is exposed during an exposure process. In someembodiments, the mask black border region 32 is a portion of the maskframe region 30 that is adjacent to the mask image region 20.

In some embodiments, where the mask 10 is a phase shift mask, the mask10 includes absorptive regions (for example, the regions formed by anabsorption layer 124), which absorb light incident thereon, andreflective regions (for example, the regions formed by a reflectivemultilayer coating 120), which reflect light incident thereon. Theabsorptive regions can be configured to reflect light incident thereonwith a phase different than light reflected by the reflective regions,such that resolution and image quality of the pattern transferred to awafer such as a wafer 40 of FIG. 5 can be enhanced. The reflective andabsorptive regions of the mask 10 are patterned such that lightreflected from the reflective regions (and, in some cases, theabsorptive regions) projects onto the wafer and transfers the pattern ofthe mask image region 20 to the wafer.

In some embodiments, as shown in FIG. 1B, the mask 10 includes asubstrate 110, a reflective multilayer coating 120, an absorption layer124 and the absorption part 128. The substrate 110 has a surface 112 anda surface 114 that is opposite the surface 112. The substrate 110includes a low thermal expansion material (LTEM), such as quartz orglass. In an example, the LTEM substrate is a SiO₂—TiO₂-based glasssubstrate. The reflective multilayer coating 120 is disposed over thesubstrate 110, particularly over the surface 112 of the substrate 110.The reflective multilayer coating 120 (also referred to as a multilayermirror (MLM)) includes a number of material layer/film pairs, where eachpair includes at least two material layers having different refractiveindices. A typical number of film pairs is about twenty to about eightypairs, however, the reflective multilayer coating 120 may have anynumber of film pairs. The material of the at least two material layersis selected such that the reflective multilayer coating 120 exhibitshigh reflectivity to a particular radiation type/wavelength. In someembodiments, the reflective multilayer coating 120 includes materiallayer pairs that exhibit high reflectivity to EUV radiation. Forexample, the reflective multilayer coating 120 includesmolybdenum-silicon (Mo/Si) film pairs (in other words, each pairincludes a molybdenum layer disposed above or below a silicon layer). Inan example, the reflective multilayer coating 120 includes forty Mo/Sifilm pairs. Alternatively, the reflective multilayer coating 120includes molybdenum-beryllium (Mo/Be) film pairs, or any othercombination of material film pairs that exhibit high reflectivity at EUVwavelengths. A thickness of the reflective multilayer coating 120 may beadjusted to achieve maximum constructive interference of the EUVradiation reflected at each interface of the film pairs while achievinga minimum absorption of the EUV radiation by the reflective multilayercoating 120. A thickness of each layer of the reflective multilayercoating 120 is determined based on the type of EUV radiation andincident angle of the EUV radiation projected onto the mask 10. In someembodiments, each of the molybdenum layers and the silicon layers of theMo/Si film pairs have a thickness of about 4 nm to about 7 nm. In someembodiments, the reflective multilayer coating 120 has a thickness ofabout 210 nm to about 350 nm.

The absorption layer 124 is disposed over the buffer layer 122. Theabsorption layer 124 includes one or more layers designed to absorbradiation in the radiation type/wavelength range projected onto the mask10. In some embodiments, the one or more layers of the absorption layer124 are designed to absorb EUV radiation. The one or more layers includevarious materials, such as tantalum-containing materials (for example,Ta, TaN, TaNH, TaHF, TaHfN, TaBSi, TaB—SiN, TaB, TaBN, TaSi, TaSiN,TaGe, TaGeN, TaZr, TaZrN, other tantalum-containing materials, orcombinations thereof), chromium-containing materials (for example, Cr,CrN, CrO, CrC, CrON, CrCN, CrOC, CrOCN, other chromium-containingmaterial, or combinations thereof), titanium-containing materials (forexample, Ti, TiN, other titanium-containing material, or combinationsthereof), other suitable materials, or combinations thereof. Aconfiguration of the one or more layers (such as material composition ofthe one or more layers) is selected to provide process flexibilityduring fabrication of the mask 10. For example, etching characteristicsof the one or more layers of the absorption layer 124 provide processflexibility, which can reduce manufacturing time and costs. In someembodiments, the absorption layer 124 has a thickness of about 2 nm toabout 5 nm.

The absorption layer 124 is patterned, such that a portion of theabsorption layer 124 is disposed in the mask image region 20, and aportion of the absorption layer 124 is disposed in the mask frame region30. The portion of the absorption layer 124 in the mask image region 20defines the pattern (or design) of the layer of the integrated circuitdevice (or chip) in the mask image region 20 of the mask 10, and theportion of the absorption layer 124 in the mask frame region 30 maydefine the pattern of alignment marks in the mask frame region 30 of themask 10.

In some embodiments, a buffer layer 122 is further disposed between thereflective multilayer coating 120 and the absorption layer 124. Thebuffer layer 122 is disposed over the reflective multilayer coating 120.The buffer layer 122 includes a material that protects the reflectivemultilayer coating 120 during processing of the mask 10 (for example,during etching of the absorption layer 124 of the mask 10). In someembodiments, the buffer layer 122 includes a ruthenium-containingmaterial, such as Ru, RuNb, RuZr, RuMo, RuY, RuB, RuTi, RuLa, otherruthenium-containing material, or combinations thereof. Alternatively,the buffer layer 122 includes a chromium-containing material, such asCr, CrN, CrO, CrC, CrON, CrCN, CrOC, CrOCN, other chromium-containingmaterial, or combinations thereof. In yet another alternative, thebuffer layer 122 includes materials other than ruthenium-containingmaterials and chromium-containing materials. The buffer layer 122 mayinclude a combination of ruthenium-containing material,chromium-containing material, and other material, for example, where thebuffer layer 122 includes multiple layers. In some embodiments, thebuffer layer 122 has a thickness of about 2 nm to about 5 nm. It isnoted that, in alternative embodiments, the buffer layer 122 may be asingle layer.

In some alternative embodiments, a capping layer (not shown) may bedisposed over the reflective multilayer coating 120 and between thereflective multilayer coating 120 and the buffer layer 122. The cappinglayer includes a silicon-containing material, such as silicon. In anexample, the capping layer is a silicon layer of a topmost Mo/Si filmpair of the reflective multilayer coating 120. The capping layer canprevent oxidation of the reflective multilayer coating 120, for example,during processing of the mask 10. The capping layer may thus include amaterial, other than a silicon-containing material, that preventsoxidation of the reflective multilayer coating 120. In an example, thecapping layer has a thickness of about 4 nm to about 7 nm. In somealternative embodiments (not shown), a conductive layer may be disposedover the substrate 110, particularly over the surface 114 of thesubstrate 110. The conductive layer includes a material that facilitateselectrostatic chucking. For example, the conductive layer includes achromium-containing material, such as Cr, CrN, CrO, CrC, CrON, CrCN,CrOC, CrOCN, other chromium-containing materials, or combinationsthereof. In some embodiments, the conductive layer is a CrN layer. In anexample, the conductive layer has a thickness of about 10 nm to about 30nm.

The absorption part 128 is disposed in a trench 126 of the reflectivemultilayer coating 120 and the absorption layer 124 in the mask blackborder region 32 adjacent to the mask image region 20 of the mask 10. Insome embodiments, the absorption part 128 is disposed in the trench 126of the reflective multilayer coating 120, the buffer layer 122, and theabsorption layer 124. In some embodiments, the absorption part 128penetrates the reflective multilayer coating 120, the buffer layer 122,and the absorption layer 124. In some embodiments, the absorption part128 is frame-shaped and surrounds the mask image region 20. In someembodiments, a width of the trench 126 ranges from 2 mm to 3 mm, and adepth of the trench 126 is larger than 300 nm, for example. Anextinction coefficient of the absorption part 128 is at least higherthan an extinction coefficient of the reflective multilayer coating 120.The absorption part 128 includes metal, oxide thereof, nitride thereofor a combination thereof. In some embodiments, the metal has anextinction coefficient larger than 0.04 measured at about 13.5 nm of alight source, such as tin (Sn), nickel (Ni), cobalt (Co), iron (Fe) or acombination thereof. The absorption part 128 includes a plurality ofnanoparticles (or nanospheres). That is, the absorption part 128 mayinclude metal nanoparticles, metal oxide nanoparticles, metal nitridenanoparticles or a combination thereof. A diameter of the nanoparticlesis less than or equal to 100 nm, for example. Since the absorption part128 includes nanoparticles which have good gap-filling ability, and theabsorption part 128 may be densely filled in the trench 126 to provide adesired reflectance. In an example, a top surface of the absorption part128 may be substantially flush with a top surface of the absorptionlayer 124.

In some embodiments, the absorption part 128 reduces reflectivity of themask black border region 32 of the mask 10, thereby reducing the amountof exposure experienced in adjacent fields 42, particularly at edges 42a of adjacent fields 42 and corners 42 b of adjacent fields 42. Suchreduction in light leakage enhances a resulting aerial image contrastrealized by the mask 10 during integrated circuit device fabrication. Inother words, the absorption part 128 minimizes reflectivity of the maskblack border region 32 of the mask 10, which can reduce shadowingeffects and mask black border effects while enhancing printability ofthe mask 10. In some embodiments, reflectivity of the mask black borderregion 32 of the mask 10 is minimized to reduce unwanted exposure. Insome embodiments, a reflectivity at the mask black border region 32 ofthe mask 10 is less than or equal to about 0.3%, particularly less thanor equal to about 0.05%, for example.

FIG. 2 is a flow chart of a method of fabricating a mask in accordancewith some embodiments of the disclosure. FIGS. 3A-3E are schematiccross-sectional views illustrating a method of fabricating a mask inaccordance with some embodiments of the disclosure. Referring to FIGS. 2and 3A, at step S210, a reflective multilayer coating 120 is formed overa substrate 110, wherein the substrate 110 includes a mask image region20 and a mask frame region 30, and the mask frame region 30 has a maskblack border region 32 adjacent to the mask image region 20. In someembodiments, the reflective multilayer coating 120 is formed on asurface 112 of the substrate 110, and a buffer layer 122 is formed onthe reflective multilayer coating 120. Then, at step S220, an absorptionlayer 124 is formed over the reflective multilayer coating 120. In someembodiments, the absorption layer 124 is formed on the buffer layer 122.In some embodiments, the reflective multilayer coating 120, the cappinglayer 122 and the absorption layer 124 may be formed by various methods,including physical vapor deposition (PVD) processes (for example,evaporation and DC magnetron sputtering), plating processes (forexample, electrodeless plating or electroplating), chemical vapordeposition (CVD) processes (for example, atmospheric pressure CVD(APCVD), low pressure CVD (LPCVD), plasma enhanced CVD (PECVD), or highdensity plasma CVD (HDPCVD)), ion beam deposition, spin-on coating,metal-organic decomposition (MOD), other suitable methods, orcombinations thereof.

Referring to FIGS. 2 and 3B, at step S230, the absorption layer 124 ispatterned in the mask image region 20. In some embodiments, by using apatterned photoresist layer, portions of the absorption layer 124 in themask image region 20 are removed, and a pattern (or design) of a layerof an integrated circuit device is formed in the absorption layer 124 inthe mask image region 20.

Referring to FIGS. 2, 3C and 3D, at step S240, a trench 126 is formed inthe reflective multilayer 120 and the absorption layer 124 in the maskblack border region 32. In some embodiments, as shown in FIG. 3C, apatterned photoresist layer 130 is formed over the patterned absorptionlayer 124. Openings 132 within the patterned photoresist layer 130expose portions of the absorption layer 124 in the mask black borderregion 32 of the mask 10. The patterned photoresist layer 130 is aradiation-sensitive photoresist layer (also referred to as a photoresistlayer, photosensitive layer, patterning layer, imaging layer, and lightsensitive layer) that is responsive to an exposure process. Thepatterned photoresist layer 130 includes a positive-type resist materialor a negative-type resist material, and may have a multi-layerstructure. The patterned photoresist layer 130 is formed by any suitablemethod. In some embodiments, a photoresist layer is deposited over thepatterned absorption layer 124, for example, by a spin-on coatingprocess; exposed to an electron beam (electron beam (e-beam)lithography); and developed such that either exposed or unexposedportions of the photoresist layer remain to form the patternedphotoresist layer 130. Such process may include a baking process (suchas a post-exposure baking process and/or a pre-exposure baking process),a rinsing process, other suitable process, or combinations thereof.Alternatively, the patterned photoresist layer 130 is formed by exposingthe photoresist layer to radiation using a mask. In yet anotheralternative, the patterned photoresist layer 130 is formed by exposingthe photoresist layer to an ion-beam or other suitable method.

Then, as shown in FIG. 3D, by using the patterned photoresist layer 130as a mask, portions of the reflective multilayer 120, the buffer layer122, and the absorption layer 124 are removed to form the trench 126,which exposes the substrate 110. In some embodiments, the trench 126 isformed in the mask black border region 32 adjacent to the mask imageregion 20. The trench 126 is entirely disposed in the mask black borderregion 32 and surrounds the mask image region 20, for example. In someembodiments, the exposed portions of the absorption layer 124, thebuffer layer 122 and the reflective multilayer 120 in the mask blackborder region 32 of the mask 300 are sequentially removed by differentetching processes. In some embodiments, imperfect etching profile suchas undercut, residue defect and/or taper profile may be occurred. Forexample, in some alternative embodiments, a sidewall of the trench 126in the reflective multilayer 120 and a sidewall of the trench 126 in theabsorption layer 124 may be not aligned, or residue of at least one ofthe reflective multilayer 120 and the absorption layer 124 may bedisposed in the trench 126.

In some embodiments, the etching process includes a dry etching process,a wet etching process, or combination thereof. The dry and wet etchingprocesses have etching parameters that can be tuned, such as etchantsused, etching temperature, etching solution concentration, etchingpressure, source power, RF bias voltage, RF bias power, etchant flowrate, and other suitable parameters. In some embodiments, the etchingprocess for the absorption layer 124 is a dry etching process. Forexample, the etching process uses a fluorine-containing gas (such asCHF₃, CF₄, and C₂F₆, other fluorine-containing gas, or combinationsthereof) and a chlorine-containing gas (such as Cl₂, SiCl₄, HCl, CCl₄,CHCl₃, other chlorine-containing gas, or combinations thereof). In anexample, the etching process uses a mixture of CHF₃ and CF₄, the processchamber pressure is 0.5 to 1.5 mTorr, the plasma source power (W_(s)) is350 to 450 W, and the substrate bias power (W_(b)) is 50 to 150 W. In anexample, the etching process uses a mixture of Cl₂ and Ar, the processchamber pressure is 1.5 to 2.5 mTorr, the plasma source power (W_(s)) is75 to 125 W, and the substrate bias power (W_(b)) is 20 to 30 W. In someembodiments, the etching process for the buffer layer 122 is a dryetching process. For example, the etching process uses afluorine-containing gas (such as CHF₃, CF₄, and C₂F₆, otherfluorine-containing gas, or combinations thereof) or anoxygen-containing gas (such as O₂, other oxygen-containing gas, orcombinations thereof). In an example, the etching process uses a mixtureof CHF₃ and Ar, the process chamber pressure is 3 to 4 mTorr, the plasmasource power (W_(s)) is 350 to 450 W, and the substrate bias power(W_(b)) is 50 to 125 W. In an example, the etching process uses amixture of Cl₂ and O₂, the process chamber pressure is 3 to 4 mTorr, theplasma source power (W_(s)) is 700 to 900 W, and the substrate biaspower (W_(b)) is 50 to 70 W. In some embodiments, the etching processfor the reflective multilayer 120 is a dry etching process. For example,the etching process uses a fluorine-containing gas (such as CHF₃, CF₄,and C₂F₆, other fluorine-containing gas, or combinations thereof) and anoxygen-containing gas (such as O₂, other oxygen-containing gas, orcombinations thereof). In an example, the etching process uses a mixtureof Cl₂, O₂, He and N₂, the process chamber pressure is 3 to 5 mTorr, theplasma source power (W_(s)) is 700 to 900 W, and the substrate biaspower (W_(b)) is 50 to 70 W.

Referring to FIGS. 2 and 3E, at step S250, an absorption material 134 isfilled in the trench 126, so to form an absorption part 128 of FIGS. 1Aand 1B. In some embodiments, the absorption material 134 is formed by acoating process such as a spin-coating process, for example. In anexample, a solvent is provided, and then nanoparticles of the absorptionmaterial 134 are dispersed in the solvent, so as to form a mixture. Insome embodiments, the solvent may be any solvent which does not reactwith the nanoparticles of the absorption material 134, has goodcoatability and may be easily removed by spinning. Then, with graduallyincreasing rotational speed such as ranging from 500 to 3000 rpm, themixture is coated over the substrate 110 to fill the absorption material134 in the trench 126, and then the solvent is removed. In someembodiments, a thickness of the coating may be controlled by therotational speed. In some embodiments, the absorption material 134 notonly fills up the trench 126 in the reflective multilayer 120, thebuffer layer 122 and the absorption layer 124 but also fills up theopening 132 within the photoresist layer 130.

Then, the photoresist layer 130 is removed, and the absorption part 128and thus the mask 10 of FIGS. 1A and 1B are formed. In some embodiments,the photoresist layer 130 is removed by a wet stripping, plasma ashing,or other known or to-be-developed technique. During the removal processfor the photoresist layer 130, a portion of the absorption material 134outside the trench 126 may be also removed, such as a portion of theabsorption material 134 filled in the opening 132 within the photoresistlayer 130. In other words, additional process for removing theabsorption material 134 outside the trench 126 is omitted. In someembodiments, as shown in FIG. 1B, a top surface of the photoresist layer130 is substantially flush with a top surface of the absorption part128, for example.

FIG. 4 is a flow chart of a method of fabricating a mask in accordancewith some embodiments of the disclosure. FIG. 5 is a top schematic viewof a wafer that is exposed using the mask of FIGS. 1A and 1B inaccordance with some embodiments of the disclosure. Referring to FIGS.1A, 1B and 4 , at step S310, an extreme ultraviolet (EUV) mask 10 havinga mask image region 20 and a mask frame region 30 is provided, whereinthe mask frame region 30 has a mask black border region 32 adjacent tothe mask image region 20, the mask image region 20 of the EUV mask 10includes a pattern of an integrated circuit device (as shown in FIG.1B). In some embodiments, details of the extreme ultraviolet (EUV) mask10 are described above, and thus are omitted.

Referring to FIGS. 1A, 1B, 4 and 5 , at step S320, a wafer 40 is exposedto EUV radiation using the EUV mask 10, wherein the pattern of the maskimage region 20 of the EUV mask 10 is transferred to the wafer 40 duringthe exposing. In some embodiments, a photoresist layer (not shown) isformed on a material layer of the wafer 40, and a portion of thephotoresist layer is exposed by the EUV mask 10. Then, the EUV radiationand a development process are sequentially performed on the photoresistlayer. After that, an etching process is performed to remove the portionof the photoresist layer if the photoresist layer is a positivephotoresist, and thus the underlying material layer is partially exposedby the photoresist layer. Then, an etching process is performed on thematerial layer by using the patterned photoresist layer as a mask, toform a patterned material layer having a pattern. In other words, duringthe exposure process, light (radiation) is projected onto the mask 10,and a portion of the light is transmitted to the photoresist layer onthe wafer 40, thereby transferring the pattern of the mask image region20 to the photoresist layer on the wafer 40. Then, the pattern of thephotoresist layer is transferred to the material layer of the wafer 40.In an example, the EUV radiation has a wavelength of about 1 nm to about100 nm. The mask image region 20 can be transferred to the wafer 40multiple times using multiple exposures with the mask 10. For example,in FIG. 2 , the mask 10 is used in multiple exposure processes topattern the wafer 40, such that the pattern of the mask image region 20is transferred to various fields 42 of the wafer 40. Each field 42corresponds to at least one semiconductor device (or at least oneintegrated circuit device) and represents an area of the wafer 40 thatwill be processed at a given time. For example, an exposure tool (suchas a stepper or a scanner) processes one field (such as exposing a field42 of the wafer 40 to the mask 10), then processes the next field (suchas exposing another field 42 of the wafer 40 to the mask 10), and so on.In some embodiments, the wafer 40 includes a photoresist layer disposedover a substrate, where the pattern of the mask image region 20 istransferred to the photoresist layer.

Conventionally, during the exposure process of each field 42, exposurelight may leak to adjacent fields 42, particularly at edges 42 a andcorners 42 b of the fields 42. Such light leakage can be attributed tolight diffraction phenomenon, positional accuracy of the mask 10 withrespect to the wafer 40, positional accuracy of the mask 10 with respectto the exposure tool, other phenomena, or combinations thereof. Lightleakage may result from positional accuracy of the mask 10 with respectto the exposure tool, such as the stepper or the scanner. For example,for each exposure process, the exposure tool defines a portion of themask 10 for exposing light thereon. An exposure slit of the exposuretool (defined by blades of the exposure tool, in an example) may definethe portion of the mask 10 that will be exposed to the light. Ideally,the light exposes the mask image region 20 of the mask 10. Typically,however, the exposure slit will expose an area of the mask 10 outsidethe mask image region 20. Generally, the mask black border region 32 ofthe mask 10 represents an area of the mask 10 that is outside the maskimage region 20 and will be exposed to the light (in other words, anarea of the mask 10 outside the mask image region that is not covered bythe exposure tool). If the mask black border region 32 of the mask 10 isexposed to light during the exposure process, the mask black borderregion 32 undesirably transmits a portion of light to the wafer 40,resulting in edges 42 a of the fields 42 receiving double exposure andcorners 42 b of the fields 42 receiving quadruple exposure. However, insome embodiments, by disposing an absorption part 128 in the mask blackborder region 32, the mask 10 reduces reflectivity of the mask blackborder region 32, thereby reducing the amount of exposure experienced inadjacent fields 42, particularly at edges of adjacent fields 42 andcorners of adjacent fields 42. Such reduction in light leakage enhancesa resulting aerial image contrast realized by the mask 10 duringintegrated circuit device fabrication.

In some embodiments, the absorption part is formed in the trench in themask black border region of the mask, to minimize reflectivity of lightat the mask black border region of the mask. Therefore, the impact onthe critical dimension (CD) nearby the image border (edge) due to theunwanted exposure may be also minimized. In addition, since the trenchis filled with the absorption material, the imperfect etching profilesuch as undercut, residue defect and/or taper profile would beacceptable. Thus, the concern to the trench profile and defect in thetrench may be not required. Furthermore, the formation of the absorptionpart is compatible with the current reticle process flow. In someembodiments, the absorption part includes metallic nanoparticles withgood electrical conduction and may be used to reduce surface chargeeffect, and thus the bridges for reducing electrostatic discharging(ESD) are not necessary and the complicated design thereof is omitted.Accordingly, cost and time for forming the mask can be significantreduced, and the quality of the mask can be improved.

In accordance with some embodiments of the disclosure, a mask includes asubstrate, a reflective multilayer coating, an absorption layer and anabsorption part. The substrate includes a mask image region and a maskframe region, wherein the mask frame region has a mask black borderregion adjacent to the mask image region. The reflective multilayercoating is disposed over the substrate. The absorption layer is disposedover the reflective multilayer coating. The absorption part is disposedin the reflective multilayer and the absorption layer in the mask blackborder region.

In accordance with alternative embodiments of the disclosure, a methodof forming a mask includes the following steps. A reflective multilayercoating is formed over a substrate, wherein the substrate comprises amask image region and a mask frame region, and the mask frame region hasa mask black border region adjacent to the mask image region. Anabsorption layer is formed over the reflective multilayer coating. Theabsorption layer is patterned in the mask image region. A trench isformed in the reflective multilayer and the absorption layer in the maskblack border region. An absorption material is filled in the trench toform an absorption part.

In accordance with yet alternative embodiments of the disclosure, amethod of manufacturing a semiconductor device includes the followingsteps. An extreme ultraviolet (EUV) mask is provided, the mask has amask image region and a mask frame region, and the mask frame region hasa mask black border region adjacent to the mask image region, the maskimage region of the EUV mask includes a pattern of an integrated circuitdevice. The EUV mask includes a substrate, a reflective multilayercoating, an absorption layer and an absorption part. The reflectivemultilayer coating is disposed over the substrate. The absorption layeris disposed over the reflective multilayer coating. The absorption partis disposed in the reflective multilayer and the absorption layer in themask black border region. A wafer is exposed to EUV radiation using theEUV mask, wherein the pattern of the mask image region of the EUV maskis transferred to the wafer during the exposing.

In accordance with some embodiments of the disclosure, a mask includes asubstrate, a reflective multilayer, an absorption layer and anabsorption part. The substrate includes a mask image region and a maskframe region, wherein the mask frame region has a mask black borderregion adjacent to the mask image region. The reflective multilayer isdisposed over the substrate. The absorption layer is disposed over thereflective multilayer. The absorption part is disposed in the reflectivemultilayer and the absorption layer and in the mask black border region,wherein an entire top surface of the absorption part is substantiallyflush with a top surface of the absorption layer.

In accordance with some embodiments of the disclosure, a mask includes asubstrate, a reflective layer, an absorption layer and an absorptionlayer. The substrate includes a mask black border region. The reflectivelayer is disposed over the substrate. The absorption layer is disposedover the reflective layer. The absorption part penetrates through theabsorption layer and disposed in the mask black border region, wherein atop width of the absorption part is substantially the same as a bottomwidth of the absorption part.

In accordance with some embodiments of the disclosure, a method ofmanufacturing a mask includes the following steps. A reflectivemultilayer is formed over a substrate, wherein the substrate includes amask image region and a mask frame region, and the mask frame region hasa mask black border region adjacent to the mask image region. Anabsorption layer is formed over the reflective multilayer. Theabsorption layer is patterned in the mask image region. A trench isformed in the reflective multilayer and the absorption layer in the maskblack border region. A mixture having a solvent and nanoparticles in thesolvent is formed. The trench is filled with the mixture to form anabsorption part in the trench.

In accordance with some embodiments of the disclosure, a mask includes areflective layer, an absorption layer and an absorption part. Theabsorption layer is disposed over the reflective multilayer. Theabsorption part is disposed in the reflective layer and the absorptionlayer, wherein an entire top surface of the absorption part issubstantially flush with a top surface of the absorption layer.

In accordance with some embodiments of the disclosure, a mask includes areflective layer, an absorption layer and an absorption part. Theabsorption layer is disposed over the reflective layer. The absorptionpart penetrates through the absorption layer, wherein a top width of theabsorption part is substantially the same as a bottom width of theabsorption part.

In accordance with some embodiments of the disclosure, a method offorming a mask includes following steps. An absorption layer is disposedover a reflective layer. A trench is formed in the absorption layer. Thetrench is filled with a plurality of nanoparticles, to form anabsorption part in the trench.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the disclosure.Those skilled in the art should appreciate that they may readily use thedisclosure as a basis for designing or modifying other processes andstructures for carrying out the same purposes and/or achieving the sameadvantages of the embodiments introduced herein. Those skilled in theart should also realize that such equivalent constructions do not departfrom the spirit and scope of the disclosure, and that they may makevarious changes, substitutions, and alterations herein without departingfrom the spirit and scope of the disclosure.

What is claimed is:
 1. A mask, comprising: a reflective layer; anabsorption layer over the reflective multilayer; and an absorption part,disposed in the reflective layer and the absorption layer, wherein anentire top surface of the absorption part is substantially flush with atop surface of the absorption layer.
 2. The mask of claim 1, wherein theabsorption part penetrates through the reflective layer and theabsorption layer.
 3. The mask of claim 1, wherein a material of theabsorption part is different from a material of the absorption layer. 4.The mask of claim 1, wherein the absorption part comprises tin (Sn),nickel (Ni), cobalt (Co), iron (Fe) or a combination thereof.
 5. Themask of claim 1, further comprising a buffer layer disposed between thereflective layer and the absorption layer, wherein the absorption partis further disposed in the buffer layer.
 6. The mask of claim 1, whereinthe absorption part is disposed in a mask black border region, and theabsorption part is filled between a portion of the absorption layer in amask image region and a portion of the absorption layer in a mask frameregion.
 7. The mask of claim 1, wherein a bottom surface of theabsorption part is substantially coplanar with a bottom surface of thereflective layer.
 8. A mask, comprising: a reflective layer; anabsorption layer over the reflective layer; and an absorption part,penetrating through the absorption layer, wherein a top width of theabsorption part is substantially the same as a bottom width of theabsorption part.
 9. The mask of claim 8, wherein the absorption partfurther penetrates through the reflective layer.
 10. The mask of claim8, wherein the absorption part has a substantially constant thickness.11. The mask of claim 8, wherein the absorption part has an extinctioncoefficient larger than 0.04.
 12. The mask of claim 8, furthercomprising a substrate below the reflective layer, wherein theabsorption layer is in direct contact with a top surface of thesubstrate.
 13. The mask of claim 8, wherein the absorption partcomprises a plurality of nanoparticles.
 14. The mask of claim 13,wherein the nanoparticles include metal nanoparticles, metal oxidenanoparticles, metal nitride nanoparticles or a combination thereof. 15.The mask of claim 13, wherein a diameter of the nanoparticles is lessthan or equal to 100 nm.
 16. A method of forming a mask, comprising:forming an absorption layer over a reflective layer; forming a trench inthe absorption layer; and filling the trench with a plurality ofnanoparticles, to form an absorption part in the trench.
 17. The methodof claim 16, wherein the nanoparticles include metal nanoparticles,metal oxide nanoparticles, metal nitride nanoparticles or a combinationthereof.
 18. The method of claim 16, wherein filling the trench with thenanoparticles comprises filling the trench with a mixture comprising asolvent and the nanoparticles in the solvent, the solvent does not reactwith the nanoparticles, and the solvent is removed after filling thetrench with the mixture.
 19. The method of claim 18, wherein forming thetrench comprises: forming a photoresist layer over the absorption layer;and using the photoresist layer as a mask, removing portions of theabsorption layer and the reflective layer to form the trench.
 20. Themethod of claim 19, further comprising removing the photoresist layerand the mixture outside the trench by a resist stripping process.